Catheter system for stenting bifurcated vessels

ABSTRACT

A stenting system includes a stent delivery catheter having a catheter shaft with a step balloon mounted thereon. The step balloon has a proximal portion and a distal portion, wherein the proximal portion is inflatable to a larger expanded diameter than the distal portion. A two-part stent has a proximal part that is mounted on the proximal portion of the step balloon and a distal part that is mounted on the distal portion of the step balloon and a non-link zone between the proximal part and the distal part of the two-part stent. The proximal part and the distal part of the two-part stent are each configured with stent struts that extend like interdigitating fingers into the non-link zone to provide improved strut coverage in the carina region of the bifurcated vessel. The non-link zone effectively eliminates any difficulties in alignment of the two parts relative to one another during placement of the two-part stent in a bifurcated vessel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Utility ApplicationSer. No. 11/107,393, filed Apr. 15, 2005, which is acontinuation-in-part of U.S. Utility Application Ser. No. 10/833,494,filed Apr. 27, 2004, which claims the benefit of U.S. ProvisionalApplication, Ser. No. 60/512,259, filed Oct. 16, 2003, and U.S.Provisional Application, Ser. No. 60/534,469, filed Jan. 5, 2004, thedisclosures of which are incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to catheters and cathetersystems for performing angioplasty and vascular stenting. Moreparticularly it relates to a catheter system and method for stenting avessel at a bifurcation or sidebranch of the vessel.

BACKGROUND OF THE INVENTION

The following patents and patent applications relate to catheters andcatheter systems for performing angioplasty and stenting of bifurcatedvessels. These and all patents and patent applications referred toherein are incorporated by reference in their entirety.

-   U.S. Pat. No. 6,579,312 Stent and catheter assembly and method for    treating bifurcations-   U.S. Pat. No. 6,540,779 Bifurcated stent with improved side branch    aperture and method of making same-   U.S. Pat. No. 6,520,988 Endolumenal prosthesis and method of use in    bifurcation regions of body lumens-   U.S. Pat. No. 6,508,836 Stent and catheter assembly and method for    treating bifurcations-   U.S. Pat. No. 6,494,875 Bifurcated catheter assembly-   U.S. Pat. No. 6,475,208 Bifurcated catheter assembly-   U.S. Pat. No. 6,428,567 Stent and catheter assembly and method for    treating bifurcations-   U.S. Pat. No. 6,387,120 Stent and catheter assembly and method for    treating bifurcations-   U.S. Pat. No. 6,383,213 Stent and catheter assembly and method for    treating bifurcations-   U.S. Pat. No. 6,371,978 Bifurcated stent delivery system having    retractable sheath-   U.S. Pat. No. 6,361,544 Stent and catheter assembly and method for    treating bifurcations-   U.S. Pat. No. 6,325,826 Extendible stent apparatus-   U.S. Pat. No. 6,264,682 Bifurcated stent delivery system having    retractable sheath-   U.S. Pat. No. 6,258,073 Bifurcated catheter assembly-   U.S. Pat. No. 6,254,593 Bifurcated stent delivery system having    retractable sheath-   U.S. Pat. No. 6,221,098 Stent and catheter assembly and method for    treating bifurcations-   U.S. Pat. No. 6,210,380 Bifurcated catheter assembly-   U.S. Pat. No. 6,165,195 Stent and catheter assembly and method for    treating bifurcations-   U.S. Pat. No. 6,142,973 Y-shaped catheter-   U.S. Pat. No. 6,117,117 Bifurcated catheter assembly-   U.S. Pat. No. 6,086,611 Bifurcated stent-   U.S. Pat. No. 5,720,735 Bifurcated endovascular catheter-   U.S. Pat. No. 5,669,924 Y-shuttle stent assembly for bifurcating    vessels and method of using the same-   U.S. Pat. No. 5,613,980 Bifurcated catheter system and method-   U.S. Pat. No. 6,013,054 Multifurcated balloon catheter-   U.S. Pat. No. 4,896,670 Kissing balloon catheter-   U.S. Pat. No. 5,395,352 Y-adaptor manifold with pinch valve for an    intravascular catheter-   U.S. Pat. No. 6,129,738 Method and apparatus for treating stenoses    at bifurcated regions-   U.S. Pat. No. 6,544,219 Catheter for placement of therapeutic    devices at the ostium of a bifurcation of a body lumen-   U.S. Pat. No. 6,494,905 Balloon catheter-   U.S. Pat. No. 5,749,825 Means method for treatment of stenosed    arterial bifurcations-   U.S. Pat. No. 5,320,605 Multi-wire multi-balloon catheter-   U.S. Pat. No. 6,099,497 Dilatation and stent delivery system for    bifurcation lesions-   U.S. Pat. No. 5,720,735 Bifurcated endovascular catheter-   U.S. Pat. No. 5,906,640 Bifurcated stent and method for the    manufacture and delivery of same-   U.S. Pat. No. 5,893,887 Stent for positioning at junction of    bifurcated blood vessel and method of making-   U.S. Pat. No. 5,755,771 Expandable stent and method of delivery of    same-   US 20030097169A1 Bifurcated stent and delivery system-   US 20030028233A1 Catheter with attached flexible side sheath-   US 20020183763A1 Stent and catheter assembly and method for treating    bifurcations-   US 20020156516A1 Method for employing an extendible stent apparatus-   US 20020116047A1 Extendible stent apparatus and method for deploying    the same-   US 20020055732A1 Catheter assembly and method for positioning the    same at a bifurcated vessel-   WO 9944539A2 Dilatation and stent delivery system for bifurcation    lesions-   WO 03053507 Branched balloon catheter assembly-   WO 9924104 Balloon catheter for repairing bifurcated vessels-   WO 0027307 The sheet expandable trousers stent and device for its    implantation-   FR 2733689 Endoprosthesis with installation device for treatment of    blood-vessel bifurcation stenosis

SUMMARY OF THE INVENTION

The present invention relates generally to catheters and cathetersystems for performing angioplasty and vascular stenting. Moreparticularly it relates to a catheter system and method for stenting avessel at a bifurcation or sidebranch of the vessel.

In a first aspect, the invention comprises a catheter system forstenting bifurcated vessels. The catheter system includes a firstballoon catheter, a second balloon catheter and a linking device forholding the first and second balloon catheters in a side-by-sideconfiguration and aligned with one another along a longitudinal axis.The catheter system may include one or more vascular stents of variousconfigurations mounted on the first and/or second balloon catheters. Thelinking device allows the catheter system to be advanced as a unit andhelps prevent premature or inadvertent dislodgement of the stent fromthe catheters. Typically, the catheter system will also include a firstand second steerable guidewire for guiding the first and second ballooncatheters within the patient's blood vessels. Optionally, the linkingdevice may also be configured to hold one or both of the guidewiresstationary with respect to the catheter system. The catheter system maybe arranged with the inflatable balloons in a side-by-side configurationfor stenting the bifurcated vessels using a method similar to the“kissing balloons” technique. Alternatively, the catheter system may bearranged with the inflatable balloons in a low-profile staggered ortandem configuration for stenting the bifurcated vessels using amodified “kissing balloons” technique. When arranged in the staggered ortandem configuration, the second balloon catheter may optionally beconstructed with a flexible tubular extension that extends the guidewirelumen distally from the inflatable balloon.

In one preferred embodiment of a catheter system for stenting bifurcatedvessels, a first balloon catheter and a second balloon catheter are heldtogether with a linking device with the first and second dilatationballoons arranged in a low-profile tandem configuration. The secondballoon catheter has an elongated flexible tubular extension extendingdistally from the second dilatation balloon. The balloon material of thefirst dilatation balloon mounted on the first balloon catheter is foldedaround the flexible tubular extension of the second balloon catheterwith only the distal tip of the flexible tubular extension exposed. Astent is crimped over the first dilatation balloon of the first ballooncatheter and the flexible tubular extension of the second ballooncatheter. Preferably, the distal tip of the flexible tubular extensionemerges from the folds of the balloon material at an intermediateposition on the dilatation balloon and extends through an open cellbetween two struts on the crimped stent. This configuration provides asmoother, more consistent surface for crimping the stent onto, whichresults in a smoother crossing profile for the catheter system.Optionally, any of the described embodiments of the catheter system maybe provided with a chromium-cobalt alloy stent with a strutconfiguration optimized for stenting bifurcations.

In a second aspect, the invention comprises a linking device for holdingthe first and second balloon catheters of the system in a side-by-sideconfiguration and aligned with one another along a longitudinal axis.The linking device allows the catheter system to be advanced as a unitand helps prevent premature or inadvertent dislodgement of the stentfrom the catheters. Optionally, the linking device may also beconfigured to hold one or both of the guidewires stationary with respectto the catheter system. The linking device is preferably releasable sothat one or both of the balloon catheters and/or the guidewires can bereleased from the linking device and maneuvered separately from the restof the catheter system. In one embodiment the linking device isself-releasing in the sense that the linking device demounts itself fromthe first and second balloon catheters as the catheter system isadvanced into the patient's body.

In a third aspect, the invention comprises a method for stentingbifurcated vessels utilizing the described catheter system. In a firstvariation of the method, the inflatable balloons are arranged in aside-by-side configuration for stenting the bifurcated vessels in amethod similar to the “kissing balloons” technique, but utilizing alinking device for holding the first and second balloon catheters in aside-by-side configuration and aligned with one another along alongitudinal axis. In a second variation of the method, the inflatableballoons are arranged in a staggered or tandem configuration forstenting the bifurcated vessels using a modified “kissing balloons”technique that also utilizes a linking device for holding the first andsecond balloon catheters in a side-by-side configuration and alignedwith one another along a longitudinal axis. When desired, the linkingdevice may be released so that one or both of the balloon cathetersand/or the guidewires can be maneuvered separately from the rest of thecatheter system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of a catheter system for stentingbifurcated vessels according to the present invention.

FIG. 2 shows the catheter system of FIG. 1 in use for stenting abifurcated vessel with a bifurcated stent.

FIG. 3 shows a variation of the catheter system of FIG. 1 for stenting abifurcated vessel.

FIG. 4 shows the catheter system of FIG. 3 in use for stenting abifurcated vessel.

FIG. 5 shows a second embodiment of a catheter system for stentingbifurcated vessels.

FIGS. 6A-9 show various embodiments of a linking device for use with thecatheter system of the present invention.

FIGS. 10-13 show the catheter system of FIG. 5 in use for stenting abifurcated vessel using a main stent and a sidebranch stent.

FIG. 14 shows a third embodiment of a catheter system for stentingbifurcated vessels.

FIG. 15 shows a cross section of a split-tube linking device for thecatheter system of FIG. 14.

FIG. 16 shows an alternate cross section of a split-tube linking devicefor the catheter system of FIG. 14.

FIG. 17 shows the catheter system of FIG. 14 in use.

FIG. 18 shows a distal portion of a catheter system for stentingbifurcated vessels.

FIG. 19 shows a bifurcated vessel after stenting with the cathetersystem of FIG. 18.

FIG. 20 shows a distal portion of a fourth embodiment of a cathetersystem for stenting bifurcated vessels prior to mounting a stent on thefirst balloon catheter.

FIGS. 21A, 21B and 21C show cross sections of the catheter system forstenting bifurcated vessels taken along section lines A, B and C in FIG.20.

FIG. 22 shows the catheter system for stenting bifurcated vessels ofFIG. 20 with a main vessel stent mounted on the dilatation balloon ofthe first balloon catheter.

FIG. 23 illustrates a stent configured for stenting bifurcated vesselsshown with the stent laid out flat to show the strut configuration ofthe stent.

FIGS. 24A, 24B and 24C are detail drawings of three portions of thestent of FIG. 23.

FIG. 25 illustrates another stent configured for stenting bifurcatedvessels shown with the stent laid out flat to show the strutconfiguration of the stent.

FIGS. 26A, 26B and 26C are detail drawings of three portions of thestent of FIG. 25.

FIG. 27 illustrates a two-part stent configured for stenting bifurcatedvessels shown with the stent mounted on a stent delivery catheter.

FIG. 28 is an enlarged detail drawing showing the non-linked zone of thetwo-part stent shown in FIG. 27.

FIG. 29 shows the two-part stent of FIG. 27 in an expanded state.

FIG. 30 shows the two-part stent of FIG. 27 expanded in a bifurcatedvessel.

FIG. 31 shows the bifurcated vessel after stenting with the two-partstent of FIG. 27.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a first embodiment of the catheter system 100 of thepresent invention for stenting bifurcated vessels. The catheter system100 includes a first balloon catheter 102 and a second balloon catheter104. An inflatable balloon 130, 132 is mounted on each of the first andsecond balloon catheters 102, 104 near the distal end of the catheters.A balloon-expandable vascular stent 150 is mounted on the cathetersystem 100, typically by crimping or swaging the stent 150 over both ofthe inflatable balloons 130, 132. The stent structure is showngenerically and is not intended to be limited to any particular strutgeometry. Typically, the catheter system 100 will also include a firstand second steerable guidewire 140, 142 for guiding the first and secondballoon catheters 102, 104 within the patient's blood vessels. The firstand second steerable guidewires 140, 142 will typically have a diameterof 0.010-0.018 inches (approximately 0.25-0.46 mm), preferably 0.014inches (approximately 0.36 mm). A linking device 160 releasably joinsthe first balloon catheter 102 and the second balloon catheter 104together near the proximal ends of the catheters. The linking device 160holds the first and second balloon catheters 102, 104 in a side-by-sideconfiguration and aligned with one another along a longitudinal axis.The linking device 160 allows the catheter system 100 to be advanced asa unit and helps prevent premature or inadvertent dislodgement of thestent 150 from the catheters. Optionally, the linking device 160 mayalso be configured to hold one or both of the guidewires 140, 142stationary with respect to the catheter system 100.

The first and second balloon catheters 102, 104 may be of any knownconstruction for balloon angioplasty or stent delivery catheters,including rapid exchange and over-the-wire catheter constructions. In aparticularly preferred embodiment, the first and second ballooncatheters are constructed as rapid exchange catheters, wherein aproximal section 106, 108 of each catheter is constructed of hypodermictubing, which may be formed from stainless steel, a superelasticnickel-titanium or titanium-molybdenum alloy or the like. The exteriorof the proximal section 106, 108 is preferably coated with PTFE oranother highly lubricious coating. A proximal connector 122, 124, suchas a luer lock connector or the like, is attached at the proximal end ofthe proximal section 106, 108 and communicates with a balloon inflationlumen that extends through the hypodermic tubing. Each catheter includesa flexible distal section 110, 112 joined to the proximal section 106,108. Typically, the flexible distal section 110, 112 has two lumens thatextend through most of its length, including a guidewire lumen thatextends from a proximal guidewire port 114, 116 to a distal port 118,120 at the distal end of the catheter, and a balloon inflation lumenthat connects from the balloon inflation lumen of the proximal section106, 108 to the interior of the inflatable balloon 130, 132, which ismounted near the distal end of the flexible distal section 110, 112. Thefirst and second inflatable balloons 130, 132 may have the same lengthand diameter and pressure compliance or they may have different lengths,diameters and/or pressure compliances, depending on the geometry of thetarget vessel that the catheter system 100 is intended for. Theinflatable balloons 130, 132 may be made from a variety of knownangioplasty balloon materials, including, but not limited to, PVC,polyethylene, polyolefin, polyamide, polyester, PET, PBT, and blends,alloys, copolymers and composites thereof. The first and secondinflatable balloons 130, 132 may be made from the same material ordifferent materials. The flexible distal section 110, 112 is typicallyconstructed of flexible polymer tubing and may have a coaxial ormultilumen construction. Preferably, one, two or more radiopaque markersare mounted on the flexible distal section 110, 112 to indicate thelocation of the inflatable balloons 130, 132 under fluoroscopic imaging.A transition element may be included to create a gradual transition instiffness between the proximal section 106, 108 and the flexible distalsection 110, 112, and to avoid a stress concentration at the juncturebetween the two sections. The transition element may be constructed as atapered or spiral wound element that is formed as an extension of thehypodermic tubing or from a separate piece of wire or tubing.

In this illustrative example, the catheter system 100 is configured fordelivering a Y-shaped bifurcated stent 150. The bifurcated stent 150 hasa main trunk 152 connected to first and second sidebranches 154, 156 ofthe stent. The catheter system 100 is prepared for use by inserting theinflatable balloons 130, 132 in a deflated and folded state through themain trunk 152 of the bifurcated stent 150, with one balloon extendinginto each of the first and second sidebranches 154, 156. The bifurcatedstent 150 is then crimped or swaged over the inflatable balloons 130,132. A support wire may be inserted into each of the guidewire lumens tosupport them during the crimping or swaging step. The proximal sections106, 108 of the catheters are inserted into the linking device 160 tohold the first and second balloon catheters 102, 104 in a side-by-sideconfiguration and aligned with one another along a longitudinal axis.This preparation may be carried out at the manufacturing facility or itmay be performed at the point of use by a medical practitioner.

FIG. 2 shows the catheter system 100 of FIG. 1 in use for stenting abifurcated vessel. The catheter system 100 is inserted into a body lumenthat is desired to be stented and advanced to the point of thebifurcation. For stenting coronary arteries or carotid arteries, thecatheter system 100 is typically inserted through a guiding catheterthat has been previously positioned at the ostium of the target vessel.For stenting in peripheral arteries or other body lumens, the cathetersystem 100 may be inserted directly into the vessel, for example usingthe Seldinger technique or an arterial cutdown, or it may be insertedthrough an introducer sheath or guiding catheter placed into the vessel.The first and second balloon catheters 102, 104 are maneuvered with thehelp of the steerable guidewires 140, 142 so that the first and secondinflatable balloons 130, 132, with the first and second sidebranches154, 156 of the stent 150 mounted thereon, extend into the respectivefirst and second sidebranches of the bifurcated vessel. The first andsecond inflatable balloons 130, 132 are inflated separately and/ortogether to expand the stent 150 and to seat it securely within thevessel, as shown in FIG. 2. This is similar to the “kissing balloons”technique that has been previously described in the literature. Anadvantage of the present invention over prior methods is that thelinking device 160 allows the catheter system 100 to be advanced as aunit and helps prevent premature or inadvertent dislodgement of thestent 150 from the catheters.

Once the stent 150 has been deployed, both balloons 130, 132 aredeflated and the catheter system 100 is withdrawn from the patient.Alternatively, one or both of the balloon catheters 102, 104 can bereleased from the linking device 160 and used separately for dilatingand/or stenting other vessels upstream or downstream of the stent 150.

FIG. 3 shows a variation of the catheter system 100 of the presentinvention for stenting a bifurcated vessel. The construction of thecatheter system 100 is very similar to the catheter system describedabove in connection with FIG. 1 with the exception that the systemutilizes a straight, i.e. non-bifurcated, stent 170. The stent structureis shown generically and is not intended to be limited to any particularstrut geometry. In one particularly preferred embodiment, the stent 170is in the form of an open-cell stent, having a cylindrical body 174 withone or more side openings 172 that are suitable for placement at abifurcation or sidebranch of the vessel without hindering blood flowinto the sidebranch. Because of their flexibility and open structure,open-cell stents are well suited for stenting bifurcated vessels. Theside openings 172 can be expanded or remodeled with a dilatation ballooninserted through the side opening or with two dilatation balloons, usingthe “kissing balloons” technique. A closed-cell stent with large sideopenings and/or expandable side openings may also be utilized.Alternatively, the catheter system may utilize a side-hole stentintended for stenting bifurcations or for stenting a main vessel at thelocation of a sidebranch vessel. In this case, the stent has anapproximately cylindrical body with a side hole intended to bepositioned at the site of a sidebranch vessel. The side hole may bepreformed in the stent or it may be a slit or a potential hole that canbe expanded to form a side hole.

The catheter system 100 is prepared for use by inserting the inflatableballoons 130, 132 in a deflated and folded state into the stent 170,with the first balloon 130 extending all the way through the cylindricalbody 174 and the second balloon 132 exiting the cylindrical body 174 atthe side opening 172 that is intended to be positioned at thebifurcation or sidebranch vessel. Alternatively, the second balloon 132may be positioned proximal to the side opening 172 so that only thedistal tip of the catheter 104 or only the guidewire 142 exits thecylindrical body 174 at the side opening 172 to decrease the distalcrossing profile of the catheter system 100. The stent 170 is thencrimped or swaged over the inflatable balloons 130, 132. A support wiremay be inserted into each of the guidewire lumens to support them duringthe crimping or swaging step. The proximal sections 106, 108 of thecatheters are inserted into the linking device 160 to hold the first andsecond balloon catheters 102, 104 in a side-by-side configuration andaligned with one another along a longitudinal axis. This preparation maybe carried out at the manufacturing facility or it may be performed atthe point of use by a medical practitioner.

FIG. 4 shows the catheter system 100 of FIG. 3 in use for stenting abifurcated vessel. The catheter system 100 is inserted into a body lumenthat is desired to be stented and advanced to the point of thebifurcation. For stenting coronary arteries or carotid arteries, thecatheter system 100 is typically inserted through a guiding catheterthat has been previously positioned at the ostium of the target vessel.For stenting in peripheral arteries or other body lumens, the cathetersystem 100 may be inserted directly into the vessel, for example usingthe Seldinger technique or an arterial cutdown, or it may be insertedthrough an introducer sheath or guiding catheter placed into the vessel.The first and second balloon catheters 102, 104 are maneuvered with thehelp of the steerable guidewires 140, 142 so that the first and secondinflatable balloons 130, 132, with the stent mounted thereon, extendinto the respective first and second sidebranches of the bifurcatedvessel. The first inflatable balloon 130 will typically be positioned inthe larger of the two sidebranches or in the main lumen of the vessel atthe location of a smaller sidebranch vessel. The first inflatableballoon 130 is inflated to expand the stent and to seat it securelywithin the vessel, as shown in FIG. 4. Then, the first inflatableballoon 130 is deflated and the second inflatable balloon 132 isinflated to expand the side opening 172 at the location of the secondsidebranch vessel. Optionally, the first and second inflatable balloons130, 132 may be inflated simultaneously using the “kissing balloons”technique.

Once the stent 170 has been deployed, both balloons 130, 132 aredeflated and the catheter system 100 is withdrawn from the patient.Alternatively, one or both of the balloon catheters 102, 104 can bereleased from the linking device 160 and used separately for dilatingand/or stenting other vessels upstream or downstream of the stent 170.Optionally, a sidebranch stent may be placed in the second sidebranchvessel before or after deployment of the stent 170.

FIG. 5 shows a second embodiment of the catheter system 100 for stentingbifurcated vessels. The construction of the catheter system 100 is verysimilar to the catheter system described above in connection with FIGS.1 and 3, with the exception that the second balloon catheter 104 isconstructed with a flexible tubular extension 134 connected to thedistal end of the catheter. The guidewire lumen extends through theflexible tubular extension 134. The flexible tubular extension 134allows the first and second inflatable balloons 130, 132 to be assembledtogether in a staggered or tandem initial position. This variation ofthe catheter system 100 utilizes a main stent 170, which is typically astraight, i.e. non-bifurcated, stent, as described above. In addition,the catheter system 100 may optionally utilize a sidebranch stent 178.The stent structures are shown generically and are not intended to belimited to any particular strut geometry. These distal features of thecatheter system 100 can be seen in greater detail in the enlarged viewof FIG. 10.

The catheter system 100 is prepared for use by first inserting thesecond inflatable balloon 132 in a deflated and folded state through theoptional sidebranch stent 178 and crimping or swaging the sidebranchstent 178 over the second inflatable balloon 132. Alternatively, thesidebranch stent 178 may be mounted on a separate balloon catheter foruse with the catheter system 100. The first inflatable balloon 130 isthen inserted in a deflated and folded state into the main stent 170,with the first balloon 130 extending all the way through the cylindricalbody 174. The flexible tubular extension 134 of the second ballooncatheter 104 is inserted into the main stent 170 alongside the firstballoon 130 with the flexible tubular extension 134 exiting thecylindrical body 174 at the side opening 172 that is intended to bepositioned at the bifurcation or sidebranch vessel. Preferably, theflexible tubular extension 134 terminates at the side opening 172 of themain stent 170 to reduce the crossing profile of the distal portion ofthe stent 170. Alternatively, the flexible tubular extension 134 mayextend distally from the side opening 172 if desired. The main stent 170is then crimped or swaged over the first inflatable balloon 130 and theflexible tubular extension 134. A support wire may be inserted into eachof the guidewire lumens to support them during the crimping or swagingstep. The proximal sections 106, 108 of the catheters are inserted intothe linking device 160 to hold the first and second balloon catheters102, 104 in a side-by-side configuration and in a desired alignment withone another along the longitudinal axis. This preparation may be carriedout at the manufacturing facility or it may be performed at the point ofuse by a medical practitioner.

In an alternate embodiment of the catheter system 100 of FIG. 5, thesecond balloon catheter 104 may be constructed without a flexibletubular extension 134. In this case, the distal tip of the secondballoon catheter 104 would be positioned proximal to the main stent 170and the second steerable guidewire 142 would be inserted into the mainstent 170 alongside the first balloon 130 with the guidewire 142 exitingthe cylindrical body 174 at the side opening 172. This would provide aneven lower crossing profile for the catheter system 100.

FIGS. 6A-9 show various embodiments of a linking device 160 for use withthe catheter system 100 of the present invention. FIG. 6A shows an endview and 6B shows a front view of a first embodiment of a linking device160. The linking device 160 has a body 162 with a first channel 164 anda second channel 166 extending along a surface of the body in aside-by-side configuration, preferably with the first and secondchannels 164, 166 approximately parallel to one another. The first andsecond channels 164, 166 are preferably undercut and sized to have acaptive interference fit with the proximal sections 106, 108 of thefirst and second balloon catheters 102, 104. The linking device 160 ispreferably molded of a flexible polymer or elastomer with a highcoefficient of friction so that it effectively grips the proximalsections 106, 108 of the first and second balloon catheters 102, 104when they are inserted into the first and second channels 164, 166. Inuse, the linking device 160 holds the first and second balloon catheters102, 104 arranged in a side-by-side configuration and aligned with oneanother along a longitudinal axis. The linking device 160 allows thecatheter system 100 to be advanced as a unit and helps prevent prematureor inadvertent dislodgement of the stent from the catheters. When it isdesired, one or both of the balloon catheters 102, 104 can be releasedfrom the linking device 160 and maneuvered separately from the rest ofthe catheter system 100.

Optionally, the linking device 160 of FIG. 6B may also be configured tohold one or both of the guidewires 140, 142 stationary with respect tothe catheter system 100. In this case, the body 162 of the linkingdevice 160 would include one or two slots 168, shown in dashed lines inFIG. 6B, that are sized and configured to create a captive interferencefit with the proximal section of the guidewires 140, 142. FIG. 6C showsan end view of the linking device 160 with optional slots 168 forholding the guidewires 140, 142. When it is desired, the guidewires 140,142 can be released from the linking device 160 and maneuveredseparately from the rest of the catheter system 100.

In an alternative embodiment, the linking device 160 of FIGS. 6A-6B maybe permanently attached to one of the balloon catheters and releasablyattached to the other. In another alternative embodiment, the linkingdevice 160 may be configured to attach instead to the proximalconnectors 122, 124 of the balloon catheters 102, 104 or it may bemolded into the proximal connectors 122, 124.

FIG. 7A shows an end view and 7B shows a front view of a secondembodiment of the linking device 160. The linking device 160 has a body162 with a first channel 164 and a second channel 166 extending alongone surface of the body in a side-by-side configuration, preferably withthe first and second channels 164, 166 approximately parallel to oneanother. The first and second channels 164, 166 are preferably undercutand sized to have a captive sliding fit with the proximal sections 106,108 of the first and second balloon catheters 102, 104. A first lockingdevice 180 is associated with the first channel 164, and a secondlocking device 182 is associated with the second channel 166. The firstand second locking devices 180, 182 are configured to releasably lockthe proximal sections 106, 108 of the first and second balloon catheters102, 104 in a desired alignment with one another along the longitudinalaxis. Each of the locking devices 180, 182 will typically include aspring or other biasing member to hold the locking device in a lockedposition and a push button or other actuating member to release thelocking device. The linking device 160 allows the catheter system 100 tobe advanced as a unit and helps prevent premature or inadvertentdislodgement of the stent from the catheters. When it is desired, one orboth of the locking devices 180, 182 can be released to allow one of theballoon catheters 102, 104 to be advanced or retracted with respect tothe other to adjust their longitudinal alignment. In addition, one orboth of the balloon catheters 102, 104 can be released completely fromthe linking device 160 and maneuvered separately from the rest of thecatheter system 100.

Optionally, the linking device 160 of FIGS. 7A-7B may also be configuredto hold one or both of the guidewires 140, 142 stationary with respectto the catheter system 100. In this case, the body 162 of the linkingdevice 160 would include one or two additional locking devices, or slotsor other structures configured to grip the proximal section of theguidewires 140, 142. When it is desired, the guidewires 140, 142 can bereleased from the linking device 160 and maneuvered separately from therest of the catheter system 100.

In an alternative embodiment, the linking device 160 of FIGS. 7A-7B maybe permanently attached to one of the balloon catheters and releasablyattached to the other.

FIG. 8A shows an end view and 8B shows a front view of a thirdembodiment of the linking device 160. The linking device 160 has a firstlinking member 184 attached to the proximal section 106 of the firstballoon catheter 102 and a second linking member 186 attached to theproximal section 108 of the second balloon catheter 104. The firstlinking member 184 and the second linking member 186 have interlockingfeatures so that the two catheters can be releasably attached to oneanother. In the example shown, the interlocking features arecorresponding male 187 and female 185 elements that can be attached anddetached to one another in the manner of a snap or zip-lock device. FIG.8C shows an end view of the linking device 160 with the first linkingmember 184 and the second linking member 186 detached from one another.Optionally, the linking device 160 can be configured so that the ballooncatheters 102, 104 can be attached to one another in differentlongitudinal alignments. In other embodiments, the linking device 160 ofFIGS. 8A-8C may utilize alternative interlocking features such asclamps, snaps, hook-and-loop fasteners, a releasable adhesive, arepositionable adhesive, etc.

Optionally, the linking device 160 of FIGS. 8A-8C may also be configuredto hold one or both of the guidewires 140, 142 stationary with respectto the catheter system 100. In this case, one or both of the linkingmembers 184, 186 would include a locking device, slot or other structureconfigured to hold the proximal section of one of the guidewires 140,142. This configuration would allow each guidewire and balloon catheterpair to be moved as a unit separately from the rest of the cathetersystem 100 when the linking members 184, 186 are separated. When it isdesired, one or both of the guidewires 140, 142 can be released from thelinking members 184, 186 and maneuvered separately from the rest of thecatheter system 100.

FIG. 9 shows a fourth embodiment of the linking device 160 that utilizesa peel-away sheath 190 for attaching the proximal sections 106, 108 ofthe first and second balloon catheters 102, 104 together. The peel-awaysheath 190 may be made from heat shrink polymer tubing that is heatshrunk onto the proximal sections 106, 108 of the first and secondballoon catheters 102, 104 to lock them together in a desired alignmentwith one another along the longitudinal axis. The peel-away sheath 190has tabs or handles 196 to facilitate peeling the peel-away sheath 190apart to release the balloon catheters 102, 104 so that they can bemaneuvered separately from one another. The peel-away sheath 190 mayutilize features, such as polymer orientation, perforations and/or anincised groove, to assure that the peel-away sheath 190 will peel apartalong a longitudinal dividing line.

FIGS. 10-13 show the catheter system 100 of FIG. 5 in use for stenting abifurcated vessel using a main stent 170 and a sidebranch stent 178. Thecatheter system 100 is inserted into a body lumen that is desired to bestented and advanced to the point of the bifurcation. For stentingcoronary arteries or carotid arteries, the catheter system 100 istypically inserted through a guiding catheter that has been previouslypositioned at the ostium of the target vessel. For stenting inperipheral arteries or other body lumens, the catheter system 100 may beinserted directly into the vessel, for example using the Seldingertechnique or an arterial cutdown, or it may be inserted through anintroducer sheath or guiding catheter placed into the vessel. Thestaggered or tandem initial position of the first and second inflatableballoons 130, 132 provides a very low crossing profile. The low crossingprofile allows the catheter system 100 with a 3.0 or 3.5 mm (expandeddiameter) coronary stent 170 mounted on it to be delivered through a 6French (approximately 2 mm external diameter) guiding catheter, whichwill typically have an internal diameter of 0.066-0.071 inches(approximately 1.68-1.80 mm internal diameter).

The catheter system 100 is maneuvered with the help of the steerableguidewires 140, 142 so that the first inflatable balloon 130, with themain stent 170 mounted on it, extends into the first sidebranch of thebifurcated vessel and the second steerable guidewire 142 extends intothe second sidebranch, as shown in FIG. 10. The first inflatable balloon130 will typically be positioned in the larger of the two sidebranchesor in the main lumen of the vessel at the location of a smallersidebranch vessel.

When advancing the catheter system 100, the second steerable guidewire142 may be positioned with its distal tip withdrawn into the flexibletubular extension 134 of the second balloon catheter 104 until thecatheter system 100 reaches the bifurcation so that it will not beinadvertently damaged or interfere with advancement of the cathetersystem 100. This can be facilitated by inserting the proximal section ofthe second guidewire 142 into the optional slot or locking device 168 onthe linking device 160. When the distal tip of the second ballooncatheter 104 is in the vicinity of the sidebranch vessel, the secondsteerable guidewire 142 can be released from the linking device 160 andadvanced with its distal tip extending from the flexible tubularextension 134 to engage the sidebranch vessel.

Once the main stent 170 is in the desired position, the first inflatableballoon 130 is inflated to expand the main stent 170 and to seat itsecurely within the vessel, as shown in FIG. 11. Then, the firstinflatable balloon 130 is deflated and the linking device 160 isreleased so that the second balloon catheter 104 can be advanced intothe second sidebranch. The second inflatable balloon 132 is inflated toexpand the sidebranch stent 178 and to seat it securely within thesecond sidebranch vessel, while simultaneously opening the side opening172 in the main stent 170, as shown in FIG. 12. Alternatively, if asidebranch stent is not used or if it is to be delivered on a separateballoon catheter, the second inflatable balloon 132 is inflated to openthe side opening 172 in the main stent 170 at the location of the secondsidebranch vessel. Optionally, the first and second inflatable balloons130, 132 may be inflated simultaneously using the “kissing balloons”technique.

Once the stents 170, 180 have been deployed, both balloons 130, 132 aredeflated and the catheter system 100 is withdrawn from the patient.Alternatively, one or both of the balloon catheters 102, 104 can bereleased from the linking device 160 and used separately for dilatingand/or stenting other vessels upstream or downstream of the main stent170. Optionally, a sidebranch stent 178 may be placed in the secondsidebranch vessel using a separate balloon catheter before or afterdeployment of the main stent 170.

FIG. 14 shows a third embodiment of a catheter system 100 for stentingbifurcated vessels utilizing a linking device 160 constructed of anelongated split-tube 200. The split-tube 200 of the linking device 160is configured to hold the proximal sections 106, 108 of the first andsecond balloon catheters 102, 104 arranged in a side-by-sideconfiguration and aligned with one another along a longitudinal axis. Alongitudinal split 202 extends the length of the split-tube 200. Thelongitudinal split 202 allows the split-tube 200 to be placed over theproximal sections 106, 108 of the catheters 102, 104 during catheterpreparation and to be removed from the catheters 102, 104 at theappropriate time during the stenting procedure. The length of thesplit-tube 200 can vary. Good results were obtained with a cathetersystem 100 having a split-tube 200 that extends along most of theproximal sections 106, 108 of the balloon catheters 102, 104 between theproximal hubs 122, 124 and the proximal guidewire ports 114, 116 of therapid exchange catheters. Preferably, the split-tube 200 of the linkingdevice 160 is configured with a distal pull-tab 210 or other feature tofacilitate lifting the distal part of the split-tube 200 to remove thelinking device 160 and release the balloon catheters 102, 104 so thatthey can be maneuvered separately from one another. The pull-tab 210 ispreferably located on a side of the split-tube 200 opposite to thelongitudinal split 202. The pull-tab 210 can be formed by skiving orcutting away part of the tube 200 as shown.

FIG. 15 shows a cross section of one embodiment of the split-tube 200 ofthe linking device 160 for the catheter system 100 of FIG. 14. Thesplit-tube 200 has an inner lumen 204 that is sized and configured tohold the proximal sections 106, 108 of the first and second ballooncatheters 102, 104 together with sufficient friction that the cathetersystem 100 can be advanced as a unit without any relative movement ofthe two catheters. In one particularly preferred embodiment, thesplit-tube 200 is manufactured as an extruded profile with anapproximately circular outer profile and an approximately oval innerlumen 204. The longitudinal split 202 connects the inner lumen 204 withthe exterior of the split-tube 200 at a thin part of the wall thatcoincides with the major axis of the oval inner lumen 204. Thelongitudinal split 202 is preferably formed during the extrusion of thesplit-tube 200. Alternatively, the tube 200 can be extruded without thelongitudinal split 202 and then slitted along the length to form thelongitudinal split 202 in a secondary operation. Suitable materials forthe split-tube 200 include polyamide copolymers (e.g. PEBAX 6333 or PA8020 from ATOFINA), polypropylene, and any extrudable medical gradepolymer with a suitable combination of strength, flexibility andfriction characteristics.

The split-tube 200 of the linking device 160 can be made with many otherpossible configurations, including single-lumen and multiple-lumenconfigurations, and may include one or more longitudinal splits 202. Byway of example, FIG. 16 shows an alternate cross section of a split-tube200 of the linking device 160 for the catheter system 100 of FIG. 14. Inthis embodiment, the split-tube 200 has a first inner lumen 206 that issized and configured to hold the proximal section 106 of the firstballoon catheter 102 and a second inner lumen 208 that is sized andconfigured to hold the proximal section 108 of the second ballooncatheter 104. The inner lumens 206, 208 are sized and configured to holdthe proximal sections 106, 108 of the first and second balloon catheters102, 104 with sufficient friction that the catheter system 100 can beadvanced as a unit without any relative movement of the two catheters.Two longitudinal splits 202 connect the inner lumens 206, 208 with theexterior of the split-tube 200. The two longitudinal splits 202 arepreferably located on the same side of the split-tube 200 opposite tothe distal pull-tab 210 to facilitate removal of the linking device 160from both catheters 102, 104 simultaneously. The longitudinal splits 202are preferably formed during the extrusion of the split-tube 200.Alternatively, the tube 200 can be extruded without the longitudinalsplits 202 and then slitted along the length to form the longitudinalsplits 202 in a secondary operation. Optionally, the linking device 160in FIG. 15 or FIG. 16 can include additional lumens, slots or otherstructures to hold one or both of the guidewires 140, 142 stationarywith respect to the catheter system 100.

FIG. 17 shows the catheter system 100 of FIG. 14 in use. The linkingdevice 160 with the split-tube 200 has the advantage that, once it isstarted, the split-tube 200 will demount itself as the catheter system100 is advanced so that the physician does not need to unpeel, remove ordisplace a linking member that would otherwise require a “third hand”.The catheter system 100 is prepared for use by aligning the first andsecond balloon catheters 102, 104 in the desired longitudinal alignmentand then pressing the longitudinal split 202 of the split-tube 200against the proximal sections 106, 108 of the catheters until they areenclosed within the inner lumen 204 (or lumens 206, 208) of thesplit-tube 200, as shown in FIG. 14. A stent or stents may then becrimped or mounted on the balloons 130, 132 in the desiredconfiguration. This preparation may be carried out at the manufacturingfacility or it may be performed at the point of use by a medicalpractitioner. The distal ends of the catheters 102, 104 with the stentor stents mounted thereon are inserted into the patient in the usualmanner through a guiding catheter with a Y-fitting 220 or otherhemostasis adapter on the proximal end of the guiding catheter. Thedistal pull-tab 210 is pulled toward the side to start demounting thesplit-tube 200 from the balloon catheters 102, 104, and then the firstand second balloon catheters 102, 104 are advanced as a unit. As shownin FIG. 17, when the split-tube 200 encounters the Y-fitting 220, thesplit-tube 200 will peel away or demount itself from the proximalsections 106, 108 of the balloon catheters 102, 104. The stent or stentscan be deployed in the vessel bifurcation using the methods describedherein.

FIG. 18 shows a distal portion of a catheter system 100 for stentingbifurcated vessels. The catheter system 100 is similar to that shown inFIG. 5 with a first balloon catheter 102 having a first inflatableballoon 130 and a second balloon catheter 104 having a second inflatableballoon 132 and a flexible tubular extension 134 extending distally fromthe balloon 132. The first and second inflatable balloons 130, 132 areassembled together in a staggered or tandem initial position as shown toprovide a low crossing profile. The catheter system 100 can use any ofthe linking devices 160 described herein to maintain the longitudinalalignment of the catheters 102, 104 during insertion. A distal stent 122is mounted on a distal portion of the first inflatable balloon 130 and aproximal stent 124 is mounted on a proximal portion of the firstinflatable balloon 130 and the flexible tubular extension 134 of thesecond balloon catheter 104. Preferably, only a small space is leftbetween the distal and proximal stents 122, 124. The distal stent 122 isconfigured to fit the distal main branch diameter and proximal stent 124is configured to fit the proximal main branch diameter and thebifurcation itself. Preferably, the proximal stent 124 is configured sothat it can be overdilated if necessary to fit the vessel at thebifurcation. In addition, the catheter system 100 may optionally utilizea sidebranch stent 178 mounted on the second balloon 132, as illustratedin FIG. 5.

The distal stent 122 and the proximal stent 124 are deployed usingsequential and/or simultaneous inflation of the first and secondinflatable balloons 130, 132 using the methods described herein. FIG. 19shows a bifurcated vessel after stenting with the catheter system 100 ofFIG. 18. Using separate distal and proximal stents 122, 124 allows thestents to be independently sized to fit the target vessel and it allowsindependent expansion of the two stents without any links between themthat could cause distortion of one or both stents during deployment.

FIGS. 20-22 illustrate a distal portion of a fourth embodiment of acatheter system 100 for stenting bifurcated vessels. The catheter system100 is similar in structure and configuration to the catheter system ofFIG. 5 with a first balloon catheter 102 having a first inflatableballoon 130 and a second balloon catheter 104 having a second inflatableballoon 132 and a flexible tubular extension 134 extending distally fromthe second inflatable balloon 132. The first and second inflatableballoons 130, 132 are assembled together in a staggered or tandeminitial position, as shown in FIG. 5, to provide a low crossing profile.The catheter system 100 can use any of the linking devices 160 describedherein to maintain the longitudinal alignment of the catheters 102, 104during insertion. In a particularly preferred embodiment, the cathetersystem 100 will utilize a linking device 160 in the form of anauto-release sheath constructed of an elongated split-tube 200, asillustrated in FIGS. 14-17.

FIG. 20 shows a distal portion of the catheter system 100 prior tomounting a stent on the first balloon catheter 102. The flexible tubularextension 134 of the second balloon catheter 104 extends distally fromthe second dilatation balloon 132 (see FIG. 5) to an intermediateposition between the proximal and distal ends of the first inflatableballoon 130. The balloon material of the first inflatable balloon 130 isfolded around the flexible tubular extension 134 of the second ballooncatheter with only the distal tip 135 of the flexible tubular extension134 exposed. This configuration provides a smoother, more consistentsurface for crimping a stent onto the first inflatable balloon 130 andthe flexible tubular extension 134, which results in a smoother crossingprofile for the catheter system 100.

FIGS. 21A, 21B and 21C show cross sections of the catheter system 100taken along section lines A, B and C in FIG. 20. FIG. 21A shows a crosssection of the catheter system 100 taken through a distal portion of thefirst inflatable balloon 130 along section line A in FIG. 20. Thisdistal portion of the first inflatable balloon 130 may be folded in anyconvenient low-profile balloon folding configuration, such as thethree-wing folding configuration shown. Alternatively, the distalportion of the first inflatable balloon 130 may be folded in a two-wingor four-wing folding configuration or other balloon foldingconfiguration known in the industry. FIG. 21C shows a cross section ofthe catheter system 100 taken through a proximal portion of the firstinflatable balloon 130 and the flexible tubular extension 134 alongsection line C in FIG. 20. In this proximal portion of the firstinflatable balloon 130, the balloon material is wrapped around theflexible tubular extension 134 completely enclosing it. Preferably, theproximal portion of the first inflatable balloon 130 is folded in atwo-wing folding configuration as shown, although other foldingconfigurations may also be used. FIG. 21B shows a cross section of thecatheter system 100 taken through a transition point intermediatebetween the proximal and distal portions of the first inflatable balloon130 along section line B in FIG. 20. At this transition point, the firstinflatable balloon 130 makes a transition from the two-wing foldingconfiguration of the proximal portion to the three-wing foldingconfiguration of the distal portion. At this transition point, thedistal tip 135 of the flexible extension tube 134 emerges from the foldsof the balloon material of the first inflatable balloon 130, as shown inFIG. 20. Optionally, the first inflatable balloon 130 may be heat set inthis folded configuration to facilitate mounting a stent on the foldedballoon in the next assembly step.

Next, a main vessel stent 170 is mounted over the first inflatableballoon 130 of the first balloon catheter 102 and the flexible tubularextension 134 of the second balloon catheter 104, as shown in FIG. 22,for example by crimping or swaging. The distal tip 135 of the flexibleextension tube 134 emerges from the folds of the balloon material of thefirst inflatable balloon 130 and extends through an open cell or sideopening 172 between two struts on the crimped stent 170. Thisconfiguration provides a smoother, more consistent surface for crimpingthe stent onto, which results in a smoother crossing profile for thecatheter system 100. Optionally, the first inflatable balloon 130 may beheat set after mounting the main vessel stent 170 onto the firstinflatable balloon 130. This provides a smoother surface on the balloonand stent assembly and increases stent retention force, which helps toprevent accidental dislodgement of the stent from the balloon.Optionally, a side branch stent 178 may be mounted on the secondinflatable balloon 132 of the second balloon catheter 104, asillustrated in FIG. 5.

In an alternate embodiment of the catheter system 100, the flexibletubular extension 134 may be a distal portion of a single or multiplelumen non-balloon catheter, which is wrapped in the balloon material ofthe first inflatable balloon 130. In another alternate embodiment of thecatheter system 100, the flexible tubular extension 134 may be asidebranch of the first balloon catheter 102, which is wrapped in theballoon material of the first inflatable balloon 130. The sidebranch ofthe first balloon catheter 102 may or may not have a second inflatableballoon mounted on it.

Optionally, any of the described embodiments of the catheter system 100may be provided with a stent with a strut configuration optimized forstenting bifurcations. FIGS. 23-26 illustrate stents 240 configured forstenting bifurcated vessels shown with the unexpanded stent laid outflat to show the strut configuration of the stent 240. Preferably, thestent 240 is fabricated from a seamless metal tube, for example by lasercutting, annealing and electropolishing. In a particularly preferredembodiment, the stent 240 is made from a high-strength biocompatiblechromium-cobalt alloy, such as alloy L605 (ASTM F90-01). Alternatively,the stent 240 may be made from other biocompatible metals or alloys,including, but not limited to, 316 stainless steel, Elgiloy or CarpenterMP35. The stent 240 is preferably configured with a multiplicity ofstruts 250 that are joined together along the length of the stent 240 bylinks 252 in an open cell configuration. The struts 250 are preferablyconfigured as sinuous or undulating rings extending circumferentiallyaround the stent 240. Each strut 250 has a predetermined number ofundulations or cells 254 around the circumference of the stent 240. Inthe embodiment shown, the cells 254 are shown as simple sinusoidalundulations, however other configurations of cells including open cellsand closed cells are also possible.

The stent 240 is divided into a distal area 242, a carina area 244 and aproximal area 246. The strut configuration in each area is preferablyoptimized for the portion of the vessel in which it will be placed. Thenumber of cells 254 in each strut 250, along with other factors,determines how much the strut 250 will be able to expandcircumferentially. In a particularly preferred embodiment, the struts250 in the carina area 244 will have a greater number of cells 254 thanthe struts 250 in the distal area 242 and the proximal area 246.Preferably, the struts 250 in the proximal area 246 will also have agreater number of cells 254 than the struts 250 in the distal area 242.This configuration allows the carina area 244 to be expanded more thanthe distal area 242 and the proximal area 246, and allows the proximalarea 246 to be expanded more than the distal area 242. The differentialexpansion properties of the different areas allow the stent 230 toconform closely to the typical geometry of a bifurcated vessel, wherethe vessel proximal to the bifurcation typically has a greater diameterthan the vessel distal to the bifurcation, and where the vessel in thecarina area immediately proximal to the carina of the bifurcation has adiameter greater than the vessels proximal or distal to the bifurcation.This configuration of the stent 240 also allows the crush resistance orhoop strength of the expanded stent to be optimized for each of theareas despite the different stent expansion ratios in each area.

An example of a 3.0 mm (expanded diameter) stent 240 is shown in FIG.23. The stent 240 is shown with the unexpanded tubular stent laid outflat to show the strut configuration of the stent as it is manufacturedand prior to crimping. The stent 240 may be formed, for example, from aseamless tube with nominal dimensions of approximately 1.60 mm diameter,with a wall thickness of approximately 0.11 mm. The stent 240 has sixstruts 250 in the distal area 242 each having six cells 254 and joinedtogether by two links 252, except for the most distal strut 250, whichis joined by three links 252, three struts 250 in the carina area 244each having eight cells 254 and joined together by four links 252, andfive struts 250 in the proximal area 246 each having seven cells 254 andjoined together by two links 252, except for the most proximal strut250, which is joined by three links 252. A single link 252 joins thedistal area 242 to the carina area 244, and three links 252 join theproximal area 246 to the carina area 244.

FIGS. 24A, 24B and 24C are detail drawings of three portions of thestent of FIG. 23. FIG. 24A shows one cell 254 of two adjacent struts 250in the distal area 242 joined by a link 252. FIG. 24B shows one cell 254of two adjacent struts 250 in the carina area 244 joined by a link 252.FIG. 24C shows one cell 254 of two adjacent struts 250 in the proximalarea 246 joined by a link 252. It will be noted that the length of thearms 256 in each cell 254 is slightly longer and more divergent in thedistal area 242, of intermediate length and divergence in the proximalarea 246 and shortest length and least divergence in the carina area 244in order to accommodate the different numbers of cells 254 in the struts250 of these three different areas. Alternatively or in addition, othermeans may be used to accommodate the different numbers of cells 254 inthe struts 250 of the three different areas. For example, the radius ofthe U-shaped bends 258 that join the arms 256 of the cells 254 togethermay be varied to accommodate the different numbers of cells 254 aroundthe circumference of the stent 240.

Another example of a 3.5 mm (expanded diameter) stent 240 is shown inFIG. 25. The stent 240 is shown with the unexpanded tubular stent laidout flat to show the strut configuration of the stent as it ismanufactured and prior to crimping. The stent 240 may be formed, forexample, from a seamless tube with nominal dimensions of approximately1.60 mm diameter, with a wall thickness of approximately 0.11 mm. Thestent 240 has six struts 250 in the distal area 242 each having eightcells 254 and joined together by two links 252, except for the mostdistal strut 250, which is joined by four links 252, three struts 250 inthe carina area 244 each having ten cells 254 and joined together byfive links 252, and five struts 250 in the proximal area 246 each havingnine cells 254 and joined together by three links 252, except for themost proximal strut 250, which is joined by five links 252. A singlelink 252 joins the distal area 242 to the carina area 244, and threelinks 252 join the proximal area 246 to the carina area 244.

FIGS. 26A, 26B and 26C are detail drawings of three portions of thestent of FIG. 25. FIG. 26A shows one cell 254 of two adjacent struts 250in the distal area 242 joined by a link 252. FIG. 26B shows one cell 254of two adjacent struts 250 in the carina area 244 joined by a link 252.FIG. 26C shows one cell 254 of two adjacent struts 250 in the proximalarea 246 joined by a link 252. Again, it will be noted that the lengthof the arms 256 in each cell 254 is slightly longer and more divergentin the distal area 242, of intermediate length and divergence in theproximal area 246 and shortest length and least divergence in the carinaarea 244 in order to accommodate the different numbers of cells 254 inthe struts 250 of these three different areas. As mentioned above, othermeans may also be used to accommodate the different numbers of cells 254in the struts 250 of the three different areas.

FIGS. 23 and 25 represent only two examples of the many possibleconfigurations for stents made according to the principles of thepresent invention. For example, the dimensions of the stent, the numberand configuration of the struts, cells and links, and other parametersof the stent can be varied greatly, while adhering to the generalprinciples of the stent design that allow it to accommodate theparticular geometry of a bifurcated vessel.

FIG. 27 illustrates a two-part stent 300 configured for stentingbifurcated vessels. The two-part stent 300 is shown mounted on a stentdelivery catheter 304 in an unexpanded condition. Preferably, the stentdelivery catheter 304 is configured with a step balloon 302 having aproximal portion 306 and a distal portion 308 that expand to differentdiameters. Typically, the proximal portion 306 will have a largerexpanded diameter than the distal portion 308, as shown in FIG. 29.However, it should be noted that the proportions of the proximal portion306 and the distal portion 308 can be reversed, for example for stentinga bifurcated vessel using a retrograde approach rather than a standardantegrade approach. The proximal portion 306 of the step balloon 302 maybe cylindrical or conical, as appropriate for the geometry of thebifurcation in the target vessel. FIG. 29 shows an example of a stepballoon 302 with a conical proximal portion 306 that increases indiameter from the proximal end of the balloon to the distal end ofproximal portion 306 and is largest in diameter adjacent to the step inthe balloon.

The two-part stent 300 has a proximal part 310 and a distal part 314 anda non-linked zone 312 between the proximal part 310 and the distal part314. FIG. 28 is an enlarged detail drawing showing the non-linked zone312 of the two-part stent 300. The proximal part 310 and the distal part314 of the two-part stent 300 are typically formed by cutting a metallictube to form zigzag or undulating stent struts 316. Alternatively, thestent struts 316 can be formed from wire. Optionally, the proximal part310 and the distal part 314 of the two-part stent 300 can be made withdifferent strut configurations, according to the principles describedabove, to accommodate expansion to different diameters in the portionsof the vessel proximal and distal to the carina region.

In a preferred configuration, the stent struts 316 form circumferentialrings that are joined to one another by one or more links similar to thestent embodiments described above. However, there are no links in thenon-linked zone 312 between the proximal part 310 and the distal part314. The absence of links in the non-linked zone 312 allows greaterfreedom of movement between the proximal part 310 and the distal part314 of the two-part stent 300. This effectively eliminates anydifficulties in alignment of the two parts relative to one anotherduring placement of the two-part stent 300 in a bifurcated vessel.

In one particularly preferred embodiment, the undulations of the stentstruts 316 extend like fingers 316, 318 from the distal end of theproximal part 310 and the proximal end of the distal part 314. Thefingers 316, 318 interdigitate with one another to create an overlap ofthe proximal part 310 and the distal part 314 in the non-linked zone312, as shown in FIG. 28, in order to provide strut coverage in thecarina region of the bifurcated vessel equivalent to or greater than atypical one-part stent.

The stent delivery catheter 304 with the two-part stent 300 can be usedas a stand-alone catheter for stenting bifurcated vessels.Alternatively, it can be used as the first balloon catheter 102 in atwo-catheter stenting system for bifurcated vessels similar to thoseshown in FIGS. 1-5, 18 and 20-22 for ease and simplicity in performing akissing-balloon technique. The tandem balloon configurations shown inFIGS. 5, 18 and 20-22 would provide the additional benefit of a lowercrossing profile, as compared to the side-by-side balloon configurationsshown in FIGS. 1-4. (or two-catheter system)

When used as a stand-alone catheter, the stent delivery catheter 304with the step balloon 302 and the two-part stent 300 allow simplestenting of a bifurcation using a provisional stenting technique. Thestent delivery catheter 304 is introduced into the patient's vascularsystem and navigated with the aid of a guidewire to the vesselbifurcation to be stented. The step balloon 302 is maneuvered so thatthe non-linked zone 312 of the two-part stent 300 is positioned at thecarina region of the bifurcation just proximal to the takeoff of thesidebranch vessel. Optionally, a second guidewire (not shown) may beintroduced into the sidebranch vessel to maintain access to thesidebranch vessel using the “jailed wire” technique. The step balloon302 is inflated with fluid to expand the two-part stent 300. FIG. 30shows the two-part stent 300 of FIG. 27 expanded in a bifurcated vessel.The proximal portion 306 of the step balloon 302 expands the proximalpart 310 of the two-part stent 300 to larger diameter appropriate to thesize of the vessel proximal to the bifurcation, and the distal portion308 of the step balloon 302 expands the distal part 314 of the two-partstent 300 to smaller diameter appropriate to the size of the vesseldistal to the bifurcation. It may be preferable to overdilate the vesselslightly, as shown in FIG. 30, because there will be some elasticrecovery of the vessel wall and the stent 300 when the balloon 302 isdeflated. After deflating and withdrawing the step balloon 302 theproximal part 310 of the two-part stent 300 will shift into the ostiumof the side branch 304 creating an access to the side branch 304. FIG.31 shows the bifurcated vessel after stenting with the two-part stent300 of FIG. 27.

According to the provisional stenting technique, the procedure may beterminated with a kissing balloon inflation and/or by deploying a stentwithin the sidebranch vessel. A third guidewire is now crossed fromwithin the proximal part 310 of the two-part stent 300 through thenon-linked zone 312 at the distal end of the proximal part 310 of thetwo-part stent 300 into the lumen of the sidebranch vessel. The edges ofthe expanded stent are designed to facilitate guidewire crossing. Afterwithdrawing the jailed wire, the procedure can be completed withclassical kissing balloons technique.

While the present invention has been described herein with respect tothe exemplary embodiments and the best mode for practicing theinvention, it will be apparent to one of ordinary skill in the art thatmany modifications, improvements and subcombinations of the variousembodiments, adaptations and variations can be made to the inventionwithout departing from the spirit and scope thereof. Although thepresent invention has been primarily described in relation toangioplasty and stenting of bifurcated blood vessels, the apparatus andmethods of the invention can also be used for other applications aswell. For example, the catheter system can be used for stentingbifurcated lumens in other organ systems of the body. In addition, thelinking devices described herein can be used in other applications whereit is desired to hold two or more catheters or similar devices arrangedin a side-by-side configuration and aligned with one another along alongitudinal axis. The principles of the invention can also be appliedto catheters other than balloon catheters.

1. A stenting system comprising: a stent delivery catheter having acatheter shaft with a step balloon mounted thereon, the step balloonhaving a stent-carrying proximal portion and a stent-carrying distalportion, wherein the proximal portion is inflatable to a larger expandeddiameter than the distal portion with a step in the diameter of the stepballoon between the stent-carrying proximal portion and thestent-carrying distal portion; a two-part stent having a proximal partthat is mounted on the proximal portion of the step balloon and a distalpart that is mounted on the distal portion of the step balloon and anon-link zone with no links or physical connections between the proximalpart and the distal part of the two-part stent.
 2. The stenting systemof claim 1, further comprising a plurality of distally-extending stentstruts extending distally from a distal end of the proximal part of thetwo-part stent and a plurality of proximally-extending stent strutsextending proximally from a proximal end of the distal part of thetwo-part stent, wherein the distally-extending stent struts on thedistal end of the proximal part of the two-part stent interdigitate withthe proximally-extending stent struts on the proximal end of the distalpart of the two-part stent within the non-link zone.
 3. The stentingsystem of claim 1, wherein the stent-carrying proximal portion of thestep balloon has a conical configuration.
 4. The stenting system ofclaim 1, wherein the stent-carrying proximal portion of the step balloonhas a conical configuration that increases in diameter from a proximalend of the balloon to a distal end of the proximal portion.
 5. Thestenting system of claim 2, wherein the two-part stent has an unexpandedcondition and an expanded condition: in the unexpanded condition, theproximal part of the two-part stent and the distal part of the two-partstent have approximately the same unexpanded diameter, and all of thedistally-extending stent struts on the distal end of the proximal partof the two-part stent interdigitate with the proximally-extending stentstruts on the proximal end of the distal part of the two-part stentwithin the non-link zone, and in the expanded condition, the proximalpart of the two-part stent has an expanded diameter that is larger thanan expanded diameter of the distal part of the two-part stent, and onlya portion of the distally-extending stent struts on the distal end ofthe proximal part of the two-part stent interdigitate with a portion ofthe proximally-extending stent struts on the proximal end of the distalpart of the two-part stent within the non-link zone.
 6. A two-part stentcomprising a proximal part and a distal part and a non-link zone with nolinks or physical connections between the proximal part and the distalpart of the two-part stent, a plurality of distally-extending stentstruts extending distally from a distal end of the proximal part of thetwo-part stent, and a plurality of proximally-extending stent strutsextending proximally from a proximal end of the distal part of thetwo-part stent, wherein the two-part stent has an unexpanded conditionand an expanded condition: in the unexpanded condition, the proximalpart of the two-part stent and the distal part of the two-part stenthave approximately the same unexpanded diameter, and thedistally-extending stent struts on the distal end of the proximal partof the two-part stent interdigitate with the proximally-extending stentstruts on the proximal end of the distal part of the two-part stentwithin the non-link zone, and in the expanded condition, the proximalpart of the two-part stent has an expanded diameter that is larger thanan expanded diameter of the distal part of the two-part stent, and onlya portion of the distally-extending stent struts on the distal end ofthe proximal part of the two-part stent interdigitate with a portion ofthe proximally-extending stent struts on the proximal end of the distalpart of the two-part stent within the non-link zone.
 7. The two-partstent of claim 6, wherein, in the expanded condition, the proximal partof the two-part stent has a conical configuration.
 8. The two-part stentof claim 6, wherein, in the expanded condition, the proximal part of thetwo-part stent has a conical configuration that increases in diameterfrom a proximal end of the proximal part of the two-part stent to thedistal end of the proximal part of the two-part stent.